Symptoms of abnormal heart rhythms are generally referred to as cardiac arrhythmias, while an abnormally rapid rhythm is referred to as a tachycardia. The present invention is concerned with the diagnosis and treatment of tachycardias, which are frequently caused by the presence of an "arrhythmogenic region" or an "accessory atrioventricular pathway" close to the inner surface of the atrium of a heart. The heart includes a number of normal pathways, which are responsible for the propagation of electrical signals from the upper chamber to the lower chamber, and which are necessary for performing normal systole and diastole function. The presence of an arrhythmogenic region or an accessory pathway in the atria can bypass or short circuit the normal pathway, potentially resulting in very rapid heart contractions, referred to here as atrial flutter. Atrial flutter is generally characterized by a saw tooth pattern with negative deflections in inferior leads of the ECG, while the atrial rate is in the range of 240-340 beats per minute.
Treatment of atrial flutter may be accomplished by a variety of approaches, including drugs, surgery, implantable pacemakers/defibrillators, and catheter ablation. While drugs may be the choice of treatment for many patients, they only mask the symptoms and do not cure the underlying causes, and they may also cause side effects. Implantable devices only correct the arrhythmia after it occurs. Surgical and catheter-based treatments, on the other hand, will actually cure the problem, usually by ablating the abnormal arrhythmogenic tissues or the accessory pathways responsible for the tachycardia.
There are, however, several drawbacks of the current mapping catheter as a device to assist in locating areas of aberrant electrical conduction for the catheter-based ablation of coronary sinus or pulmonary ostia. One of the major problems lies in the unstable positioning of the catheter inside the right atrium or about the pulmonary veins of the heart. When a catheter is not stabilized, the heart's electrical conduction pattern is difficult to map and establish. Furthermore, the catheter shall have a longitudinally stretchable/compressible soft tip portion so that the shock from contacting the catheter tip on the tissue is absorbed.
Therefore there is a need for an improved catheter having a capability of longitudinally stretchable/compressible to be used in coronary sinus mapping as a diagnostic device, and also used in coronary sinus ablation in the treatment of atrial flutter and atrial fibrillation indications.